The present invention relates to an object levitating apparatus, which levitates an object with air pressure generated from sound waves, and a method for controlling the apparatus.
Japanese Unexamined Patent Publications No. 7-24415, No. 7-137824, and No. 9-202425 each disclose an object levitating apparatus for levitating an object on a vibrating body with air pressure generated from sound waves produced by the vibrating body, which is vibrated by a vibrating means. The vibrating body used in each apparatus is plate-like. The surface of the object facing the vibrating body is flat. Object levitating apparatuses that move levitated objects by blasting air or by producing traveling waves with a vibrating body have also been disclosed.
The object levitating apparatus may be installed on a carriage to transfer an object in a levitated state.
If an object is plate-like and has a large surface area, it is preferred that a plurality of vibrating plates be used to stably levitate the object. However, when longitudinal vibrations are produced in the vibrating plates, the force for holding the objects in a predetermined position is insufficient. Therefore, the object is displaced even by a small lateral force. A vibratory device is provided for each vibrating body. If the vibrating force differs between vibrating bodies, the object will be horizontally displaced with respect to the vibrating bodies. In the object levitating apparatus that holds an object in a levitated state, the object may fall off the apparatus if the object is left in a displaced state. In an apparatus that moves an object in a levitated state with travelling waves produced by the elongated vibrating bodies, the object may meander or fall.
Therefore, a guide or a restricting member is necessary to restrict the horizontal movement of the object. However, in an apparatus for carrying an object while levitating the object by the elongated vibrating body, a large-scale guide is necessary, which increases manufacturing costs. Also, in an object levitating apparatus that holds an object in a levitated state, the guide obstructs the transfer of the object from the object levitating device.
Japanese Unexamined Patent Publication 9-202425 discloses an object levitating apparatus provided with a photosensor, which detects a levitated object approaching an end of a carrying path of the apparatus. Based on a detection signal from the sensor, the apparatus stops moving the object or shifts the carrying direction. However, it is necessary that many sensors be arranged along the long carrying path to detect the position of the object and prevent the object from moving out of the carrying path.
Accordingly, it is an object of the present invention to provide an object levitating apparatus that holds an object in a predetermined position without a guide, a restricting member, or many sensors, and a method for controlling the object levitating apparatus.
To attain the above object, the present invention provides a method of controlling, an object levitating apparatus for levitating an object on a plurality of vibrating bodies with air pressure generated from sound waves produced by the vibrating bodies. Each vibrating body is vibrated by a corresponding vibrating apparatus. Each vibrating apparatus has a oscillator and a transducer. The transducer is actuated by the oscillator to vibrate the corresponding vibrating body. The method includes determining impedance of each transducer, and controlling each oscillator in accordance with the determined impedance to restrict displacement of the levitated object.
The present invention also provides a method of controlling, an object levitating apparatus for levitating an object on a plurality of vibrating bodies with air pressure generated from sound waves produced by the vibrating bodies. Each vibrating body is vibrated by a corresponding vibrating apparatus. Each vibrating apparatus has an oscillator and a transducer. The transducer is actuated by the oscillator to vibrate the corresponding vibrating body. The method includes determining impedance of each transducer, and controlling the position of each vibrating body in accordance with the determined impedance to restrict displacement of the levitating object.
The present invention also provides a levitating apparatus for levitating an object on a plurality of vibrating bodies with air pressure generated from sound waves produced by the vibrating bodies. The apparatus comprises a vibrating apparatus for vibrating each vibrating body. Each vibrating apparatus has an oscillator and a transducer. The transducer is actuated by the oscillator to vibrate the corresponding vibrating body. A detector detects the impedance of the transducer. A controller controls each oscillator in accordance with the impedance detected by the detector to restrict displacement of the levitating object.
The present invention also provides an apparatus for levitating an object on a plurality of vibrating bodies with air pressure generated by sound waves produced by the vibrating bodies. The apparatus comprises a vibrating apparatus for vibrating each vibrating body. Each vibrating apparatus has an oscillator and a transducer. The transducer is actuated by the oscillator to vibrate the corresponding vibrating body. An elevating means raises or lowers the vibrating bodies. A detector detects the impedance of the transducer. A controller controls the elevating means to change the position of each vibrating body in accordance with the impedance detected by the detector.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example of the principles of the invention.